1. Field of the Invention
The present invention relates to a reamer, and particularly to a reamer that includes a single cutting edge.
2. Description of the Related Art
Since a reamer that has a single cutting edge is generally subjected to a load in a specific direction during reaming work, it comprises a guide pad to receive such a load in a specific direction. On the basis that the peripheral face of the guide pad contacts the inner face of a machined hole during processing, the reamer is supported relative to the machined hole. Since burnishing occurs due to the guide pad sliding against the hole, the surface roughness of the inner face of the machined hole can be improved. However, for this type of reamer, usually a large area of the peripheral face of the guide pad contacts the inner face of the machined hole, and the friction resistance between the two (burnishing torque) is increased. This would reduce the accuracy of the machining of the inner face of the machined hole.
Japanese Patent Laid-Open No. 2004-66391 discloses a tool having a single cutting edge, devised so as to improve the accuracy for a finish hole. The tool in Japanese Patent Laid-Open No. 2004-66391 includes, in a cutting part, a cutting edge, a single, substantially arc-shaped pad that is arranged to the rear of the cutting edge in the rotational direction, and a chip discharge groove. Further, in the single pad, a plurality of flutes that are longitudinally extended are formed by cutting parts of the arc-shaped face of the pad.
According to the tool of Japanese Patent Laid-Open No. 2004-66391, the single pad is arranged immediately to the rear of the cutting edge, in the rotational direction of the tool, and formed so as to extend within a continuous range. When this tool is employed to perform the reaming of a hole in a workpiece, especially a workpiece having high elasticity, the pad might push the hole radially and outwardly. In a case wherein the pad has enlarged the hole, there is a probability that the obtained inner diameter of the machined hole may be smaller than a desired size. Such enlarging of the hole by the pad would interrupt the reaming work performed using the tool, and deteriorate the accuracy of the machining of the inner face of the machined hole.